Resistance heated stopcock



Aug. 21, 1962 c. M. DE WOODY 3,050,608 RESISTANCE HEATED STOPCOCK FiledFeb. 16, 1960 IN VENTOR CHARLES M. oawooor ATTORNEY United States Patent3,050,608 RESISTANCE HEATED STOPCOCK Charles M. De Woody, Vineland,N.J., assignor to Ace Glass Incorporated, Vineland, N.J., a corporationof New Jersey Filed Feb. 16, 1960, Ser. No. 9,019 1 Claim. (Cl. 219-19)This invention relates to laboratory glassware and the like, andconsists more particularly in new and useful improvements in a stopcockwhich is heated by means of an electrical resistance coating applied toits outer surface, this application being the copending application ofthe applicant and others, Serial No. 862,331, filed December 28, 1959.

Chemical handling apparatus in the past has been plagued withcomplications in dealing with molten solids, particularly those of anorganic nature. Heat from some source is necessary to preventsolidification within the container and its connecting parts, such asstopcocks and adjacent lines. Stopcocks in particular, have beentroublesome and several methods have been employed in an effort toeliminate freezing.

For example, the container to which the stopcock is connected, as Wellas the contents thereof, have been heated to a temperature which is highenough to prevent the formation of a solid plug within the bore of thestopcock when it is closed. The higher the melting point, the greater isthe danger of decomposition of the material, and other means eventuallybecome necessary.

Also, stopcocks have been steam or vapor jacketed but this is cumbersomeand often impossible with small stopcocks. Auxiliary vaporizing meanstoo, are required which could be as large as the handling apparatus.

In another form, an electrical heating element is wrapped around thestopcock, the heating wire being either bare or covered with asbestos orbraided glass fiber insulation.

Experience has shown that the physical shape of the stopcock makes itdifiicult to wrap in order to properly heat the central portion betweenthe arms. Bare wire cannot be overlapped and is generally useless andthe Wire coverings of insulated wire, both tend to abraid in use andthey also have other disadvantages such as heat insulating quantitiesand bulk, high application costs, poor appearance, and liquid absorbencywhich makes it necessary to remove the wire when cleaning the stopcock.

It is therefore the primary object of the present invention to overcomethe disadvantages above noted in connection with conventional equipment.

An object of the invention is to provide a stopcock of glassware or thelike having an integral heating means incorporated therein in the formof a resistance coating to thereby facilitate convenience of use.

Another object of the invention is to provide a heated stopcock capableof producing higher temperatures with greater safety than is possiblewith conventional equipment.

Still another object is to provide a stopcock having a resistancecoating including shunt strips of lesser resistance material at selectedlocations to intercept the major portion of the current and redistributethe same to effect more uniform heating.

A further object is to provide a heated stopcock having a resistancecoating and an integral insulation having heat and chemical resistantproperties.

A still further object of the invention is to provide a heated stopcockdesigned to facilitate the control of normally solid or highly viscousmaterials which are frequently handled in laboratory equipment.

Another object is to provide a heated stopcock of this nature which isneat in appearance, easy to manipulate and clean, and requires lessspace than those which are heated by the use of auxiliary heating means.

With the above and other objects in view which will appear as thedescription proceeds, the invention consists in the novel featuresherein set forth, illustrated in the accompanying drawings and moreparticularly pointed out in the appended clainr.

Referring to the drawings in which numerals of like character designatesimilar parts throughout the several views:

FIGURE 1 is a view in side elevation showing one form of stopcockembodying the invention, certain areas being broken away forillustrative purposes;

FIGURE 2 is an enlarged sectional view taken on line 2-2 of FIGURE 1,showing the relationship of the resistance coating and one of theterminals; and

FIGURE 3 is a modified form of the invention including shunt strips.

As shown in the drawings, the stopcock is basically of conventionalstructure, that shown in FIGURE 1 purely for purposes of illustration,comprising a barrel 3 having integral stems or side arms 4 and 5projecting from opposite sides thereof. The stems may be plain at theirfree ends, or, as shown, one or both of the stems may carry a ball andsocket fitting 6 to facilitate connection to other pieces of laboratoryequipment.

The hollow barrel 3 is provided with a tapering bore 7 adapted toreceive the correspondingly contoured body of a plug 8, having the usualhandle or knob 9. The plug 8 is provided with a transversely drilledpassageway or port 10 adapted for alignment with the passageways 4a and5a respectively, of the stems 4 and 5. A suitable nut 11 and Washer 12retain the plug 8 in place in the barrel 3 in the usual manner.

As before indicated, the structure just described is conventional andmay comprise many known variations in stopcock design. Briefly, theinvention consists in applying to the outer periphery of a stopcock ofglassware, or similar material having a normally non-conducting surface,a film or coating of resistance material arranged in a completeconducting circuit and having terminal means adapted to receive opposedcontact members or electrodes arranged at spaced points in electricalcontact with the resistance coating.

Considering the invention in greater detail and referring to FIGURE 1, athin coating or film of electrical resistance material 13 is applied tothe periphery of both the stems 4 and 5 and the intermediate barrel 3.Preferably, the resistance coating consists of platinum applied byspraying one or more coats of a solution containing platinum and bakingin an oven at temperatures in excess of 1100 F. after the coating hasdried. The thickness of the resulting metallic platinum or platinumalloy coating may vary but generally should not exceed .0015 inch andshould not be less than .0003 inch. It will be understood that Whileplatinum is preferred, various other metals such as silver, tin,aluminum and gold may be used, the thickness of which will vary with themetal used. For instance, a coating resulting from a tin salt may be inthe order of .000016 inch.

At opposite ends of the stems 4 and 5, and at least partially overlyingthe adjacent portions of the resistance coating 13, we provide terminalbands 14 and 15 preferably consisting of coatings of silver or othermetal of less resistance than the coating 13. The thickness of theterminal bands is in the order of 0.008 inch and generally not less than.003 inch. In any event, the thickness of the terminals should begreater than that of the coating 13, and, if desired, the terminalcoatings may be of the same material as that employed in the resistancecoating, but in this case, the subsequent. coats are applied inlocalized well-defined geometric patterns. The

3 metallic coatings of the bands 14 and 15 are in electrical contactwith the adjacent areas of the resistance coating 13 and are adapted toreceive suitable contact clamps 16 on conductors 17 connected to asuitable source of electrical current.

An insulating jacket 18 overlies the resistance coating 13 and ispreferably formed by dipping the resistance coated stopcock in siliconerubber catalyzed latex and curing to a resilient form with heat, orapplying any suitable high temperature electrical insulation, such as aceramic glaze or silicone resin. Silicone rubber has been found topossess the desired insulating properties and its resilience also servesthe added purpose of protecting the stopcock against breakage. However,other materials having these properties could obviously be used.

FIGURE 3 represents a modification of the invention which under someconditions may be preferable to the one just described. In this form ofthe invention, the barrel 3, in addition to the resistance coating 13,is provided adjacent the junctions of the stems 4 and 5, withlongitudinally extending shunt strips 19 which overlie the resistancecoating 13 at these points. These shunt strips may consist of a coatingof silver or other material of lesser resistance than the coating 13,similar to the terminal bands 14 and 15. The purpose of the shunt strips19 is to intercept most of the current as it reaches these points and toredistribute the same so that the barrel is heated more uniformly. Inother words, with the form of the invention shown in FIGURE 1, thecurrent tends to flow in a straight line across the barrel, while withthe shunt strips 19, a more uniform distribution of current is efiected.

With regard to the overlying terminal bands and shunt strips describedabove, it may be noted that this arrangement possesses a distinctadvantage over certain known resistance coating methods wherein the moreconductive material employed as a bus bar is applied directly to thebase of glass and underlies the resistance coating. For example, thefact that the coefficients of expansion of terminal band material suchas silver or silver ceramic mixtures are not sufiicient matches for theglass coefficients and introduce strain at the glass surface. On theother hand, when the terminal band material is applied to and overlies acompatible noble metal surface, the ductility of the underlying metalwill tolerate differential movement.

The operation and advantages of the present invention are generallysimilar to those described in said copending application. It will beapparent that by providing an electrical resistance film or coating onthe periphery of the stopcock and arranging said coating in anelectrically conducting circuit and having terminal means for positivelylocating and retaining electrical contacts, that stopcocks of glasswareand the like may be heated under controlled and safe condition. Also, byproviding integral electrically conducting shunt strips, a controlledpattern of heat intensity is provided.

in the claim, the term glassware is intended to include glass-coated, orvitreous enameled metal and similar materials as a base for theresistance coating.

From the foregoing, it is believed that the invention may be readilyunderstood by those skilled in the art without further description, itbeing borne in mind that numerous changes may be made in the detailsdisclosed without departing from the spirit of the invention as setforth in the appended claim.

I claim:

A heated stopcock formed of glassware, comprising a barrel and at leasttwo stems, the outer surface of said barrel and stems being coated withan electrical resistance material, opposite terminal bands on saidstems, electrically connected to said coating material, and shunt stripsof a material of less resistance than said coating, formed on thecoating of said barrel adjacent the junctions of said stems forintercepting a portion of the current flowing through said coating andredistributing the same to provide uniform heating.

References Cited in the file of this patent UNITED STATES PATENTS897,782 Reilley Sept. 1, 1908 1,978,089 Jones Oct. 23, 1934 2,357,473Jira Sept. 5, 1944 2,556,557 Schweitzer June 12, 1951 2,710,900 LinderJune 14, 1955 2,761,945 Colbert Sept. 4, 1956 2,876,985 Birchall Mar.10, 1959 2,883,307 Orr Apr. 21, 1959 FOREIGN PATENTS 739,123 France Oct.24, 1932 837,426 Germany Apr. 28, 1952

